1. Field of the Invention
The present invention relates generally to switching mode power supplies, and more particularly, to a method and apparatus for reducing switching losses during standby mode in a switching mode power supply.
2. Description of the Related Art
Conventional electronic devices such as televisions, computer monitors, VCRs, etc., operate in a normal mode in which considerable power is consumed, and in a standby mode in which little power is consumed while waiting for the normal mode to resume.
Although most electronic devices consume less power in standby mode than in normal mode, most electronic devices remain in standby mode much longer than normal mode. Consequently, most countries have recently started placing restrictions on the amount of power consumed by devices in standby mode.
Conventional electronic devices attempt to reduce power consumption in standby mode by utilizing auxiliary power supplies, reducing input power, etc. However, the implementation of these methods increases the manufacturing cost considerably.
When a switching mode power supply ("SMPS") operates in standby mode, most of the input power is consumed by the switching losses of a main switch, which is coupled to the primary winding of a transformer, and by an integrated circuit (IC) which controls the operation of the main switch. Therefore, to reduce power consumption in standby mode, it would be desirable to reduce switching losses from the main switch in standby mode.